--------- Description of the helios-software for transputer use with the ATW800/2 ------------
André Saischowa, 28 May 2025

Here is the software to use Helios 1.3 on the command line or with X11. This package complements the atw800_2_basepack, which must be installed beforehand. Please copy the folder helios13 and the program helios.tos into the directory c:\atw800_2, which contains the files of the atw800_2_basepack.

helios.tos - this can be used to start Helios13. No driver needs to be installed beforehand, helios.tos does this with

host.con - Configuration file for Helios with the FPGA-T425 as root (driver is fpgabios.tos)
host.2mb - Configuration file for Helios with a TRAM/2MB in Slot 1 (driver is tbios.tos)

helios13 
- this contains the file system for using Helios on the transputer and the ioserver
- the driver for using the ATW800/2 with X11 is located in source code under local/xsrc/devices. This can be easily compiled and installed by calling make.

-------------- Helios on the ATW800/2 -----------------

Helios can be used as a single or multi-transputer system (additional hardware required), with or without X11. Here is the single transputer mode first.

Start -> Call HELIOS.TOS. If necessary, FPGABIOS.TOS is started, then IOSERVER.TTP
 After booting, the Helios console appears, where you can log in with the root login, there is no password at first. You can exit Helios with the key combination CTRL,Shift + F9 (mostly ;-) ). The server is then terminated and resetatw.tos is called. After that, any color table changed by X11 should show the usual Atari colors again. However, any programs running on the transputers will continue to run. Sometimes, however, only pressing the reset button on the Atari helps.
Helios is quite a complex piece of software, help can be found at www.transputer.net 

X11 operation
For X11 operation, you select a resolution in the range 640x480 to 1280x720, in 256 colors, when you start the Atari. X11 uses the same resolution, but uses a different memory area so that there are no conflicts with GEM.

To start X11, first start helios.tos as normal and log in with root. Entering startx should then start X11, which takes some time until you find a rectangle at the cursor for positioning the xterm. Click with the mouse to position it on the free area, then an xterm should be visible for further use. after that you can continue with the usual Unix shell commands. 

If you left-click on a free desktop area, a menu appears in whose submenu demos you can start some demo programs. Please try puzzle...

-------------- Helios - multi-transputer operation -----------------
To use Helios as a multi-transputer system, you obviously need several transputers, for example in the slots of the ATW800/2 or as an external farm. Ideally, you use the TRAM modules that Axel (https://www.geekdot.com) offers, the AM-B404. The following examples are based on this. It should be noted that Helios was created in the 1980s, and such nonsense as PlugAndPlay was unknown back then ;-) If you want to use a different topology of the transputer network, the *.map files must be recreated, this can be done manually or with the RSPY tool (call rspy -ch -m).

There are (at least) 3 ways to set up a multi-transputer system.

1. The easy way
Helios is started as a single system via HELIOS.TOS (FPGABIOS). No reconfiguration is necessary at first. After logging in as root, use one of the following commands

startns atw8_480.map // if only slot 1 is occupied
or
startns atw8_488.map // if slots 1 and 2 are occupied

This boots the slot transputers and integrates them into the network. X11 can be used. However, no task force manager is started (at least I don't know how), parallel computing of the transputers must be controlled via CDL scripts

2. The (not quite so) easy way (FPGABIOS)

Rename the Helios13/etc/initrc file to initrc.one and the Helios13/etc/initrc.net file to initrc, and activate the desired configuration in this (line with atw8_480.map or atw8_488.map). The transputer network is then activated when booting. X11 is not possible here because X11 cannot run on node 00; this is used as a resource manager for the network.

3. The more complicated but "correct" way. (TBIOS)

The FPGA-T425 is not used as the root node, but rather the TRAM in slot 1. Both slots on the ATW800/2 must be populated, or better still, an external farm must also be connected. Only then does it really make sense, because you then have several computing nodes (and not just one) available.

The following configurations must be changed (assuming that the current system is set up as a single system)

- rename helios13/host.con to host.425
- rename helios13/host.2mb to host.con
- rename helios13/etc/initrc to initrc.one
- rename helios13/etc/initrc.net to initrc, use the line with atw8_884.map in initrc

Then TBIOS.TOS is started first, then HELIOS.TOS! This is important!!!

After logging in (as root), start X11 with the startx.net command. After a while, the X11 desktop should be available. If you have at least 4 transputers in the system, you should be able to use the farmlib, which enables the "simple" distribution of programs to the individual computer transputers. See the examples in examples/farmlib.

However, working effectively with a transputer network under Helios requires certain knowledge. You cannot avoid working through the "Helios Bible", which can be found here: https://www.transputer.net/hbooks/techref/hbk.pdf.

Of course, you don't necessarily have to use Helios; you can also use the D72UNI to develop programs for transputer networks, which also usually have less communication overhead over the links. This usually leads to faster program execution. Take a look at the examples that Udo Matthe developed and adapted for the ATW800

-------------- Help and links on the subject of transputers -----------------
If you have any questions, please don't hesitate to contact me, but please note that I do all this as a hobby, I am not a transputer professional. However, there are people in our community who know more about this, first and foremost Michael Brüstle and Claus Peter Meder. With their help, I've been able to sort everything out so far. 
Regarding my configuration, I usually work with EmuTos or Magic as the OS. I run parcp (https://joy.sophics.cz/parcp/) in a VT52 terminal, which enables fast data exchange with my Mac without having to reconnect. This part is highly recommended. The transputer tools run perfectly in the VT52 terminal from Magic 
A good introduction to the subject of transputers is www.transputer.net, where you can find lots of information and documentation on the subject. There is also a separate section dedicated to Helios.

Finally, have fun (and gain knowledge) with the ATW800/2

André Saischowa
